Since a single yarn often cannot satisfy the requirements which are placed on it with regard to its strength and/or its uniformity during further processing or in the finished product, it is conventional in the textile industry for at least two yarns to be twisted together, for example, by means of a two-for-one twisting or cabling machine, wherein, however, in principle, the winding up of individual yarns is also possible in the two-for-one twisting method.
The known two-for-one twisting or cabling machines, which have been described in detail in numerous patent specifications, each comprise a plurality of identical workstations, wherein in each case, in the region of each workstation, at least one running yarn circulates around a yarn-twisting or cabling spindle in the form of a yarn balloon before it is wound by means of a spooling and winding device to form a take-up bobbin.
In the case of two-for-one twisting, for example, two yarns are connected to one another with a S or Z twist, wherein both yarns each receive an additional twist. With a workstation which operates according to the two-for-one twisting method, this means that a single or multiply folded yarn is often withdrawn upwards from a feed bobbin arranged in the protective pot of the spindle and introduced into the upper end of the hollow bobbin axle of the yarn-twisting spindle via a controllable yarn-supply unit arranged, for example, on the bobbin axle of the yarn-twisting spindle.
The folded or single yarn arrives at a rotatably mounted, driveable yarn-twist-providing element arranged below the protective pot and leaves the yarn-twist-providing element via a radial opening. The, for example, folded yarn is then guided towards a stationary balloon-yarn-guide-eye arranged above the protective pot of the spindle and accordingly forms a yarn balloon rotating around the protective pot here because of the rotation of the yarn-twist-providing element between the yarn-twist-providing element and the balloon-yarn-guide-eye arranged above the protective pot, the size of which can be adjusted by the yarn-supply unit.
Furthermore, in the case of the workstations which operate according to the two-for-one twisting method, there are various feed types with regard to the manner in which the yarns are supplied to the yarn-twisting spindle. For example, the feed yarns can originate from a feed bobbin, which is mounted in a protective pot of the yarn-twisting spindle and on which a folded supply yarn is wound, or from two feed bobbins arranged one above the other in the protective pot of the yarn-twisting spindle, from each of which a feed yarn is unwound.
In the case of the cabling method, it is known that a second yarn is wound around a first feed yarn, wherein the rotation of the single yarn remains substantially unchanged. This means that in the case of a workstation which operates according to the cabling method, two separately arranged feed bobbins are often used.
In this context, a first feed bobbin is conventionally arranged in a protective pot of the cabling spindle, while the second feed bobbin is often kept ready in a bobbin rack which is positioned above the workstation. From this feed bobbin stored in the bobbin rack, a so-called outer yarn is withdrawn, for example, by a yarn-supply unit, and introduced from below into the hollow bobbin axle of a driveable yarn-twist-providing element mounted in a rotatable manner, which is constituted, for example, as a storage disk.
The running outer yarn leaves the storage disk via a radial opening and is then guided, for example, via a so-called yarn discharge plate arranged on the storage disk, to a stationary balloon-yarn-guide-eye arranged above the protective pot, where it winds around the feed yarn of the first feed bobbin, or is cabled, as this is designated by specialists in the field.
Because of the rotation of the storage disk between the yarn discharge plate and the balloon-yarn-guide-eye arranged above the protective pot, the outer yarn forms a yarn balloon rotating around the protective pot, the size of which can be adjusted during the cabling process by the yarn-supply unit arranged in the region of the yarn pathway of the outer yarn.
After passing the stationary balloon-yarn-guide-eye, the twisted or cabled yarn is wound by a spooling and winding device onto a take-up bobbin.
In the case of the workstations of the known two-for-one twisting or cabling machines, in which the height of the circulating yarn balloon is limited in each case by a balloon-yarn-guide or respectively a balloon-yarn-guide-eye, it is often not possible or respectively extremely difficult to vary the height of the yarn balloon during the operation of the workstation.
Since there is a risk of a yarn break occurring, especially in the case of friction-sensitive yarn materials, such as polypropylene, polyester or polyacrylic, if the yarn balloon comes into contact with the stationary protective pot of the spindle during the yarn twisting or cabling process, it was initially conventional with such two-for-one twisting or cabling machines to adjust the diameter of the yarn balloon in such a manner that it is disposed safely above the diameter of the stationary protective pot.
However, since large yarn balloons are known to lead to relatively large ventilation losses and therefore to an increased energy requirement of the workstations of the two-for-one twisting or cabling machines, various attempts have already been made in the past, especially in conjunction with less friction-sensitive yarn materials, such as cotton, to reduce or respectively to limit the diameter of the yarn balloons.
In the case of a two-for-one twisting or cabling machine as described, for example in German Patent Publication DE-OS 1 813 801, the feed bobbin is arranged, for example, not protected in a stationary protective pot, but is disposed openly on a component of the two-for-one yarn-twisting spindle constituted as a bobbin carrier.
In order to avoid contact between the circulating yarn balloon supported externally on a cylindrical balloon limiter and the feed bobbin, a cylindrical yarn guide, arranged between the balloon limiter and the feed bobbin, which surrounds the feed bobbin at the height of the upper edge of the balloon limiter, is also provided in this known two-for-one yarn-twisting spindle.
However, the disadvantage with these known two-for-one yarn-twisting spindles is the relatively long physical contact of the circulating yarn balloon with the stationary balloon limiter.
Since the stresses acting on the yarn as a result of such stationary balloon limiters are relatively high, such two-for-one yarn-twisting spindles can be used only for relatively insensitive yarns.
It has therefore already been suggested that the size, that is, the diameter, of the yarn balloon can be influenced by implementing controlling or regulating interventions with regard to the yarn tension of the yarn forming the yarn balloon in the workstations of two-for-one twisting or cabling machines.
Such two-for-one twisting or cabling machines as described, for example, in German Patent Publication DE 10 2008 033 849 A1, conventionally comprise a plurality of generally identically constituted workstations arranged side-by-side.
The workstations of these known two-for-one twisting or cabling machines each comprise a stationary protective pot for the accommodation of at least one feed bobbin, a rotatably mounted yarn-twisting or cabling spindle and a unit for influencing the yarn tension, for example, a yarn-supply unit.
The workstations of these known textile machines in each case further comprise a balloon-yarn-guide arranged in a stationary manner.
Furthermore, European Patent Publication EP 2 260 132 B1 describes a twisting or cabling machine in which the rate of production of the workstations is increased through a corresponding positioning of the yarn balloon guide, but in which the quality of the yarn is not supposed to be impaired.
For this purpose, the workstations of these known textile machines are each supposed to be fitted with a vertically adjustable yarn balloon guide. However, no indications can be derived from European Patent Publication EP 2 260 132 B1 regarding the constructive constitution of the vertically adjustable yarn balloon guide. This literature reference also contains no indications of how or where the yarn balloon guides should advantageously be positioned.
However, for a considerable time, various textile devices have been known in the textile-machine industry, which allow the height of the yarn balloon to be influenced.
For example, in German Patent Publication DE 37 39 175 A1, a bobbin rack is described, in which the running behaviour of the feed bobbins is optimised in that the distance between the relevant feed bobbin and an associated balloon-yarn-guide is varied constantly during operation, in each case, dependent upon the weight of the feed bobbin.
This means that, with this known bobbin rack, either the feed bobbins or the balloon-yarn-guide-eyes are mounted in a movable manner.
Movably mounted balloon-yarn-guides or more specifically balloon-yarn-guide-eyes have also been known for a considerable time in the context of ring spinning machines.
For example, German Patent Publication DE 44 02 582 A1 describes a ring spinning machine of which the balloon-yarn-guides are mounted in a height adjustable manner, as is conventional with such textile machines. This means that the ring spinning machine comprises several machine rails arranged, in each case, one above the other on both of its longitudinal machine sides, wherein, as known, further machine rails mounted in a vertically movable manner are installed above a stationary spindle rail. In this context, the balloon-yarn-guides of the numerous workstations of the ring spinning machine are arranged on the uppermost of these machine rails, mounted in a vertically movable manner.
With such an arrangement, all of the balloon-yarn-guides on one side of the machine are displaced together during the spinning operation; a separate control of the balloon-yarn-guide of an individual workstation is not possible.
A ring spinning machine with a comparable arrangement of the balloon-yarn-guide is also known from European Patent Publication EP 1 071 837 B1. Furthermore, with this known ring spinning machine, the balloon-yarn-guides of the numerous workstations are each arranged in a tiltable manner on the associated vertically displaceable machine rail.
With such a tiltable arrangement of the balloon-yarn-guides, the access to the ring spinning spindles is supposed to be improved, and accordingly, the automation of the bobbin changing process of the ring spinning machine should be considerably improved.